Earlier this Summer one was selling around here on Craigslist for $50. I'm not sure if they got it or not, though. I think it's value on eBay would be limited because it's not collectible enough for most people to justify the shipping cost.
For your data, assuming you have an OS CD, boot from the CD, and use Drive Setup to do a low level format on your drives. If you want to be nice to the buyer, do a clean install of the OS.
If the data is super sensitive and you're really nervous, just remove the drives and destroy them.
Where are you located?